1. Field of the Invention
The present invention relates to a method of manufacturing a recording head which performs recording by discharging ink onto a recording medium.
2. Description of the Related Art
As an inkjet recording head using electrothermal conversion elements, a recording head such as the one shown in FIG. 8A has been known. In FIG. 8A, in order to facilitate understanding the structure of the recording head, part of a discharge port plate is cut away.
In the recording head shown in FIG. 8A, a recording element substrate 201 is bonded and fixed by an adhesive 203 to the upper surface of a supporting member 204. The recording element substrate 201 includes a substrate 206 provided with a plurality of groove-like ink-supplying ports 202 (three ports in FIG. 8A) and a plurality of electrothermal conversion elements 205 arrayed on both sides of each of the ink-supplying ports 202, and a discharge port plate 208 fixed on the upper surface thereof. The discharge port plate 208 has discharge ports 207 disposed at positions facing the electrothermal conversion elements 205.
Furthermore, as shown in FIG. 8B, a plurality of ink-supplying passages 209 (three passages in FIG. 8B) are disposed in the supporting member 204, and the ink-supplying passages 209 face and communicate with corresponding ink-supplying ports 202. Ink supplied to each ink-supplying passage 209 is guided to the ink-supplying port 202 and the discharge port 207. The ink filled in the discharge port 207 is discharged as ink droplets by thermal energy generated by the electrothermal conversion element 205.
In the process of manufacturing such a recording head, as a method of bonding the recording element substrate 201 to the supporting member 204, for example, a method is disclosed in Japanese Patent Laid-Open No. 9-187952. FIGS. 9A and 9B show the method disclosed in Japanese Patent Laid-Open No. 9-187952.
According to the method disclosed in Japanese Patent Laid-Open No. 9-187952, a recording element substrate is accurately positioned by a vacuum suction finger, and then the recording element substrate is fixed with an ultraviolet/thermosetting type adhesive.
First, as shown in FIG. 9A, a recording element substrate 201 held by a vacuum suction finger 212 is made to abut on the supporting member 204, and pressure is applied thereto. As a result, an adhesive 203 is squeezed out at the ends in the longitudinal direction of the recording element substrate 201 and toward the inside of an ink-supplying port 202. Then, ultraviolet light is applied by ultraviolet irradiation heads 213 and 214 from outside the vacuum suction finger 212 to the adhesive 203 squeezed out at the ends in the longitudinal direction of the recording element substrate 201. Thereby, the recording element substrate 201 is temporarily fixed.
Regarding the adhesive 203 squeezed out toward the inside of the ink-supplying port 202, during retention until the back-end process or in the thermosetting step of the uncured adhesive, which will be described later, the viscosity decreases immediately before thermosetting. At that time, in some cases, the adhesive may move along the corner inside the ink-supplying port due to capillary force and may clog discharge ports 207.
In order to prevent clogging of the discharge ports, as shown in FIG. 9B, after the vacuum suction finger is moved away, irradiation is performed by ultraviolet irradiation heads 215 and 216 perpendicularly on the discharge port plate 208 to cure the adhesive. Then, the uncured adhesive at which ultraviolet light does not sufficiently arrive is completely cured by heating. Thereby, the recording element substrate 201 is fixed on the supporting member 204.
In the back-end process, a wiring substrate is fixed on the supporting member 204 onto which the recording element substrate 201 has been bonded and fixed. The fixing of the wiring substrate is performed by heat press bonding using a thermosetting adhesive.
In the manufacturing method described above, in order to cure the adhesive 203 squeezed out toward the inside of the ink-supplying port 202, ultraviolet irradiation is performed from a direction perpendicular to the discharge port plate 208.
However, as shown in FIGS. 8A and 8B, in order to supply a sufficient amount of ink to the discharge ports 207, each ink-supplying port 202 is designed such that each of openings at the front surface and the back surface of the recording element substrate 201 has a rectangular shape, and the opening area gradually decreases from the back surface side toward the front surface side. Therefore, the adhesive 203 squeezed out toward the inside of the ink-supplying port 202 is located at recessed positions from the side to be irradiated, i.e., in the shaded regions, in the case where ultraviolet light is applied from a direction perpendicular to the discharge port plate 208. That is, as shown in FIG. 9C, even if ultraviolet irradiation is performed from a direction perpendicular to the discharge port plate 208, ultraviolet light passing through the discharge port plate 208 is not directly applied to the adhesive 203. Therefore, in the manufacturing method described above, ultraviolet light is applied to the adhesive 203 by diffused reflection inside the ink-supplying port 202 to cure the adhesive 203. In FIG. 9C, in order to facilitate understanding the adhesive squeezed out toward the inside of the ink-supplying port of the recording head, part of the discharge port plate is cut away.
When ultraviolet light reflects diffusedly inside the ink-supplying port 202, ultraviolet light attenuates greatly by the time it arrives at the squeezed-out adhesive 203. Therefore, the intensity of ultraviolet light decreases. In the case where the amount of transfer is increased due to a change in viscosity or in the case where uneven transfer occurs, the amount of the adhesive 203 squeezed out toward the inside of the ink-supplying port 202 may increase. In such a case, the adhesive 203 may not be cured sufficiently by the ultraviolet light the intensity of which is decreased due to diffused reflection.
When the adhesive 203 is not completely cured, in some cases, problems may occur. For example, as described above, the uncured adhesive 203 rises, due to capillary force, from a corner 210 in the ink-supplying port 202 along a line of intersection 211 in the ink-supplying port 202, resulting in clogging of the discharge port 207.
Furthermore, with recent trend toward higher density and higher precision of discharge ports in recording heads, a discharge port plate composed of a photosensitive resin material is required to have higher absorbance for ultraviolet light so that a desired patterned shape can be obtained. That is, since ultraviolet light passing through the discharge port plate is absorbed in a larger amount than before, the intensity of ultraviolet light which arrives at the adhesive squeezed out toward the inside of the ink-supplying port is further decreased.
When the intensity of ultraviolet light used for curing the squeezed out adhesive is decreased as described above, there may arise problems, such as clogging of discharge ports and reduction in productivity due to extension of irradiation time.